Electric resistance element and method of operating the same



March 26, 1946. s. H. STUPAKOFF 2,397,445

ELECTRIC RESISTANCE ELEMENT AND METHOD OF OPERATING THE SAME Filed March 27, 1945 INVENTOR 561710111?. Stulnakoff 4,4@ Wmv. 45t/] zwfw Patented Mu. 26, '194e'v iJNlTEDv sTATl-:s PATENT orrlce ELECTRIC RESISTANCE ELEMENT AND METHOD OPERATING THE SAME Y Semen/H. Stupako, Latrobe, Pa., assignor to Stnpakofl Ceramic & Manufacturing Co., La-

trolve, Pa., a corporation ofA Pennsylvania Application March 27, 1943, Serial No. 480,754

(c1. coi-e3) 14 Claims.

high temperature operations is limited vby two factors. The first and most serious is the comparatively low melting point of the metal 'of which the resistor is made, plus perhaps its susceptibility to oxidation, and the second is the difiiculty of supplying terminals that will withstand the high temperature and sustain a satisfactory current now. For example, one of the most satisfactoryv a resistor wherein the metallic conductor may op' erate close to its boiling point, which in most cases is several hundred degrees higher than its melting point, without destruction of the resistor, and at the same time a terminal construction is provided which will withstand high temperature operation. b According to the present invention, the metallic resistor is encased within a high temperature refractory tube equipped with water-cooled or other terminals. As the temperature of the resistor increases the metal conductor may melt and its temperature carried on up close to its boiling point. The molten metal, being confined. can not escape, and the mechanical support is provided by Y the refractory. If the refractory be a conductor of the second class, additional'heat may be generated by the flow of current through the refractory tube. When the resistor cools, the metal solidies in the tube. The refractory protects the metal from oxidation.

My invention may be more fully understood by reference to the accompanying drawing, in which:

Figure 1 is a, longitudinal section through a resistor embodying my invention and made in accordance therewith; and

Figure 2 is a transverse section in the plane of line II-II of Figure l.

According to the present invention a refractory tube 2 of appropriate length and wall thickness is formed of a highly refractory earthen body. One material which may be used is a body of steatite porcelain which retains its strength and form at very high temperatures. Other porcelain and ceramic compositions well known to those skilled in the art may be used. Steatite, moreover, may be of a variety weil known to those skilled in the art, which is a conductor of the second class, becoming itself a conductor of electricity at elevated temperatures. such material is known to the art under the tradename Insu1con.

Into the bore 3 of the refractory tube or rod 2 is inserted a rod 4 of a cross section, preferably such as to substantially ll the bore, and its ends project slightly beyond the ends of the tube. The rod may be of platinum, chromium, rubidium, tungsten, tantalu'm, or other highly refractor metal having a high melting point and a still higher boiling temperature.

Closely fitted over each end of the sheath 2 and rod 3 is a metallic terminal 5 of cup-like form. It may be of copper, aluminum, or other metal, depending upon the eiiiciency of the cooling means to be described, or may be a more refractory metal, as platinum, or other of the metals above named. Each terminal block 5 has a recess 6 to receive the end of the metal core or rod 4, and has a conductor lead 1 attached thereto. A thin metal shell 8 enclosing the exterior of each terminal provides a water `iacket or chamber 9 for cooling fluid. Connections I0 and Il provide for the iniiow and outflow of cooling fluid.

In operation, the connections are connected to a source of current. The metal core t constitutes a resistance which is heated by the flow of current therethrough. As the temperature exceeds the melting point of the metal, the ymetal may liquify but it may not escape, being confined by the refractory tube and the terminal blocks; and the liquid metal will continue to make contact with the terminal members. The terminals themselves are protected by the cooling means, and air which might'otherwise oxidize the molten metal is substantiallyv excluded; The refractory tube providesl the support for the molten metal, and it radiates heat from the metal, as it too approaches the temperature of the metal. It is of course apparent that the refractory tube 2 must have substantial strength at the temperature so created.

If the refractory body be a. conductor of the second class, the metal core will carry all of the load at lower temperatures and bring the refractory up to a conducting temperature, whemdepending upon how heavy the current and the rela- One variety of refractory also, causing the refractory to become a prime heat generating element.

While my invention is especially applicable for use in electric furnace and heating operations, the resistor may be employed also as a source of intense illumination, and my invention contemplates such use of the resistor. i

While I have illustrated one specific embodiment of my invention and have named specific materials, it will be understood that this is by way of illustration, and that various changes and modifications may be made therein.

I claim:

1. An electric resistance element comprising a refractory tubeI a metal body within the tube, and a terminal at each end of the tube contacting said body, the said metal body extending entirely through the refractory tube, and Ibecoming molten at operating temperatures, the tube having a softening temperature higher than the melting point of the metal body.

2. An electric resistance element comprising a' refractory tube, a metal body within the tube and supported throughout its length in the said refractory tube, and a terminal at each end of the tube contacting said body, the said menu body becoming molten interiorly of the tube at operating temperatures,' the terminals retaining the metal body in the tube even when the metal body is molten, the tube having a softening temperature higher than the melting point of the metal body, and means for cooling said terminals.

3. An electric resistance element comprising a refractory tube, a metal resistor extendingL lengthwise of the tube, and extending entirely through the refractory tube, the said resistor, although normally solid metal, becomes fluid at operating temperatures, a terminal sealing each end of the tube and contacting the resistor, said tube being resistant to fusing at a temperature above the fusing temperature of the :metal reslstor.

4. An electric resistance element comprising a refractory tube, a metal resistor extending lengthwise of the tube, and extending entirely through the refractory tube, the said resistor, although normally solid metal, becomes uid at operating temperatures, a terminal sealing each end of the tube and contactng the resistor, said tube being resistant to fusing at a temperature above the fusing temperature of the metal resistor and being also a conductor of the second class.

5. An electric resistance element comprising a refractory tube which is rigid at the operating temperature of the element, a conductor Within the tube coextensive with the tube, and which is normally rigid but becomes non-rigid at the temperature of operation, and a terminal sealed to each end of the tube for conning and contacting the conductor and excluding oxygen.

6. An electric resistance element comprising a refractory tube which is rigid at the operating temperature of the element, a conductor within the tube which is non-rigid at the tem-perature of operation, a terminal sealed to each end of the tube for confining and contacting the conductor and excluding oxygen, and means for cooling the terminals, and means enclosing the terminals but spaced therefrom for retaining a cooling fluid for cooling the said terminals.

7. An electric resistance element comprising a tube of steatite porcelain, a rod of refractory metal passing lengthwise through the tube coxtensive therewith and extending beyond each end thereof, and a metal terminal closing each end of the tube contacting the ends of the rod.

8. An electric resistance element comprising a tube of steatite porceclain, a rod of refractory metal passing lengthwise through the tube, and a. metal terminal closing each end of the tube contacting the ends of the rod, means for cooling the terminals, said refractory metal having a boiling temperature of 1800 C.

9. The method of operating an electric resistor comprising a refractory tube with a normally solid and rigid refractory metal rod extending lengthwise thereof through` the entire length of the tube and extending beyond the end thereof, and with a terminal sealing each end of the tube which comprises operating the resistor at a temperature at which the normally solid and rigid metal rod is rendered fluid.

10. The method 0f operating an electric resistor comprising a refractory tube with a refractory metal rod extending lengthwise thereof and with a terminal sealing each end of the tube which comprises operating the resistor at a temperature above the softening point of the metal krod and below its boiling point and cooling each of the terminals.

11. An electrical resistance element .comprising y a refractory body having a bore extending therethrough, a metal resistor mounted in the bore and extending therethrough sufficiently far to project from the refractory body at each end thereof, the said metal resistor substantially filling the bore, a metal terminal of cup-like form closely fitted over each end of the refractory body and the metal resistor, the terminals sealing the body and resistor against entry of air, a lead connected to each terminal, means enclosing each terminal for forming a cooling chamber around each terminal, and means for circulating a cooling medium through each cooling chamber for sweeping the terminals with the cooling medium.

12. An electrical resistance element comprising a refractory tubular body, a metal resistor in the said tubular body, the said metal resistor being normally solid but adapted to become molten during operation of the resistance element, the refractory tubular body having a softening temperature substantially above the melting temperature of the said metal resistor, terminals enclosing each end of the refractory tubular body and the metal resistor and forming retaining seals for each end of the refractory body and metal resistor for retaining the metal resistor in the refractory body even when the resistor is molten, while sealing the ends of the refractory body and metal resistor against admission of air, a wateriacket mounted on each end of the refractory body and enclosing the said terminals, means for continuously circulating water through the water Jackets for chilling the terminals even while the said metal resistor is molten, and leads for the terminals mounted thereon and extending through the said Water jackets.

l3.-An electrical resistance element comprising a refractory tubular body, the said tubular body being a conductor of the second class for conducting current responsively to the body being heated to conducting temperature, a metal resistor filling the said tubular body and extending therefrom at each end thereof, the said tubular body having a softening temperature substantially above the melting temperature ot the metal resistor, terminals forthe said body and resistor enclosing each end of the said body and resistor and sealing each end thereof against access of air while retaining the metal resistor in the said refractory body even when molten, a water jacket mounted on the refractory body and enclosing the said terminals, means for circulating water through said Jackets in contact with the terminals, and means for supplying vcurrent to the terminals.

14. An electric resistance element comprising a refractory tube, a metal resistor within the tube, and illling the same, the said metal resistor extending rrom the tube at each end thereof. a cupshaped terminal mounted on each end of the retractory tube and enclosing the ends of the rei'ractory tube as metal resistor, the terminal sealing the refractory tube and metal resistor against admission of air while retaining'the metal resistor in the tube even when the metal resistor is molten, a water jacket enclosing each of the terminals, means for circulating water through the water jacket in direct contact with the terminals, and a lead for each terminal secured thereto and extending through the said water jackets wherelby the terminals and leads are continuously swept by circulating cooling water passing through the water jackets.

SEMON H. AKOFF. 

